This invention relates in general to writing pens and in particular to a modular writing pen combination. The invention is modular in the sense of being comprised of modules to the extent that all of the writing pen combinations, except for a specific writing tip and ink and with a minor feed change therein, may be considered to be one module while the various writing tips may be considered other modules. This invention is considered modular being a family of modules of a broad product system. Technically this invention is a pen, however, it is intended to be a refill for use inside of a holder which together constitute a pen as commonly understood. Much of its value stems from its being a refill.
The primary objective of this invention is considered to be that of permitting a writing instrument manufacturer and marketer to provide the consumer with an array of products in a range of writing modes, such as a ball point, a soft tip, a conventional tip or other tip and a range of body or holder types which may be of different constructions, appearances, intrinsic values and prices. The products are also intended to possess certaian not-otherwise-attainable and/or desirable features such as better writing for the ball mode, a new stylus of tuf tip writing mode, writing-mode changing permissibility, a large ink supply, and servicing convenience. This invention permits a smaller total number of discrete product models than normally would be required for such an array of product characteristics -- with associated operational economies, all the way from design to dealer stocking and represents more value per unit of price paid by the consumer than commonly is economically feasible in a going business situation. This invention attains the foregoing by providing a replaceable refill, that is shipped from the factory filled with an adequate supply of ink as contrasted with a permanently embodied writing instrument sub-assembly and incorporating in that refill all of the writing-related functional elements involved in a writing instrument, such as writing composition, composition storage, flow control, and leakage control means and writing tip instead of just some of such elements. The refill is designed in such a way that all of its components except the writing tip itself, and possibly the ink, will be alike and so that the overall geometry will be the same for a number of variants providing acceptable performance in a number of different modes of writing. The refill is adapted to be fitted into a number of different holders in such a way as to permit easy interchangeability and replacement of refills, anywhere from factory to field.
In the pursuit of the objects of this invention, much attention had to be addressed to the many different requirements which each element of the system places on other elements and how each such requirement can be avoided or satisfactorily met. Examples of such different requirements are that a soft tip or a conventional nib cannot be made to perform satisfactorily with a high viscosity or "thick" ink, such as is used in the conventional ball pen, because of the comparatively great flow resistance of the high viscosity ink and the absence, in the former two writing modes, of mechanical (ball rotational) means of conveying the ink to the paper and that the means of storing, controling flow of and avoiding leakage of thick inks must be different from those of low viscosity or "thin" inks, principally for flow resistance related reasons. Another requirement is that one of the more common means of storing thin ink in soft tip products is in a capillary reservoir which will not cooperate properly with a conventional nib product also using thin ink nor with a ball point. Additionally, of course, in the pursuit of the objectives of this invention, attention was addressed to opportunities for the realization of performance gains such as that a ball point, appropriately modified to work with thin ink, will "glide" over the paper more effectively and produce a more intense and legible line than will a conventional ball pen and that a "vacuum" reservoir will permit more ink capacity per unit of volume, more complete write-out of ink, and more uniform line quality throughout write-out of a soft tip or stylus tip than will a capillary reservoir. Other examples of performance gains are that a thin-walled casing of metal for the refill provides more ink capacity and increased volume of receiving a larger collector to improve ink overflow capacity for a given refill size than would be possible with the more common thick-walled, plastic casing along with no vapor loss through the metal casing walls such as normally occurs through the plastic casings and that a replaceable refill embodying the writing tip, of whatever writing mode, minimizes usage and maintenance problems arising from the unavoidable delicateness of all, and the impermanence of many types of writing tips.
As further background it should be pointed out that standard thick ink ball pens do not make a line as intense as fountain pens and other writing instruments due to inherent design limitations caused by the use of thick, that is, relatively viscous ink. Specifically, it is not practical or desirable to design a thick ink ball pen which will apply an intense line because thick ink does not dry quickly and is easily smeared on the paper and the pen will build up excess ink on the point which can be easily transferred to the user's clothing. A further disadvantage of such a design is that seepage problems and flow control problems will become serious enough to be noticed by the user. Therefore, in order to obtain good line intensities, it is more practical to use a thin or liquid ink. That is, an ink with a viscosity of 0.9 to 10 centipoise rather than an ink of 5,000 to 25,000 centipoise. The latter ink is typical for commercially available thick ink ball pens. In order to use a thin ink it is necessary to provide a different type of flow control than the ball and seat flow control means used in most presently available ball pens. Normally, a capillary reservoir system can be used that consists of compacts of synthetic fiber which hold the ink in the reservoir due to capillarity between the fiber or a vacuum reservoir system which comprises a reservoir and a collector. The reservoir in the vacuum reservoir system is a hollow, normally tubular space in the barrel of the pen which holds the ink by virtue of a slightly negative pressure. This negative pressure is created by the design of the ink passages and air control passages which connect the reservoir to the point and the collector. The collector acts as a surge tank to temporarily hold ink expelled from the reservoir due to pressure-temperature changes. It is frequently of multifin design and holds ink by capillary attraction.